Catalytic cracking of hydrocarbons and apparatus therefor



April 3, 1951 4 R. c. LASSIAT ETAL CATALYTIC CRACKING 0F HYDROCARBONSAND APPARATUS THEREFOR 3 Sheets-Sheet 1 Filed March 2, 1946 INVENTORSmama/v0 a. LASS/AT GEORGE/1. KELSO JAMESE. EVA/V5 AGENT April 3, 1951 R.c. LASSIAT ET AL 2,547,021

CATALYTIC CRACKINGOF HYDROCARBONS AND APPARATUS THEREFOR Filed March 2,1946 s Sheets-Sheet s v I INVENTORS RAYMOND 6. L485!!! 7 GEORGE/1. KELS0 EGENT Patented Apr. 3, 1951 CATALYTIC CRACKING OF HYDROCARBONS ANDAPPARATUS THEREFOR Raymond C. Lassiat, Swarthmore, George H. Kelso,Upper Darby, and James E. Evans, Wallingford, Pa., assignors to HcudryProcess Corporation, Wilmington, Del.,

of Delaware a corporation Application March 2, 1946, Serial No. 651,662

8 Claims. 1

This invention relates to those treatments of fluids with static contactmasses where the treatment occasions a change of heat in thesystem. Theinvention is particularly concerned with the type of treatmentexemplified by a conversion of petroleum by contact with porous solidcatalysts where the operation gives rise to a net exothermic heateffect.

Since the present invention relates especially to commercial catalyticcracking operations, it will be described in terms of such operations,although it is to be understood that the invention is not restricted tosuch operations but includes other hydrocarbon conversion processes suchas reforming, dehydrogenation with or without added hydrogen, vaporphase treating of cracked gasolines and the like, other endothermiccatalytic operations, and similar processes.

An especially efiective process for the catalytic cracking ofhydrocarbons in which the hydrocarbons are contacted with a static bedof solid catalyst has been frequently described in considerable detail(see, for example, The Design and Operating Features of Houdry Fixed-BedCatalytic Cracking Units, by R. H. Newton and H. G. Shimp, Transactionsof the American Institute of Chemical Engineers, volume 41, page 197,April 25, 1945, and the references there cited). Briefly summarized, theprocess consists of passing hydrocarbon materials, such as a gas oil, aheavy naphtha, or a reduced crude, over a static or fixed bed of poroussolid catalyst in a converter provided with means for indirect heatexchange. The hydrocarbon material is catalytically cracked to highoctane gasoline, light hydrocarbons, and a" carbonaceous deposit whichremains on the catalyst. The carbonaceous deposit accumulates as thecracking continues and reduces the ability of the catalyst to functionefiiciently. Therefore, after a suitable period of time, the flow ofhydro carbon material is stopped, the converter and catalyst purged ofhydrocarbon vapors, and the catalyst is regenerated by passing air overit to burn ofi the carbonaceous deposit. The activity of the catalyst isthus restored and, after air is purged from the converter, the cycle ofoperation is repeated. Inasmuch as the exothermic heat evolved duringregeneration is greater than the endothermic heat of cracking, theexcess heat must be removed from the converter by some means. Incommercial operations, this has been done by an indirect heat exchangefluid circulated through heat exchange elements in the form of finnedimperforate conduits regularly disposed throughout the catalyst mass.

After extended periods of use such as is encountered in commercialoperations, the catalyst progressively deteriorates and must eventuallybe removed from the converter. The cause of the deterioration of thecatalyst is not fully known, although it has been found that the type ofhydrocarbon material, the partial pressure of process steam, and thetemperature of regeneration are factors. Since the converters must becooled and partially dismantled in order to change the catalyst, anappreciable length of time is consumed in the change of catalyst, duringwhich time the converter is unproductive. The time required to changethe catalyst is therefore of distinct economic importance, since theproductive capacity of the refinery will thereby be infiuenced.

According to our invention, we crack hydro carbon materials by passingthem over a fixed or static contact mass which has both catalyticactivity and high volumetric heat capacity. We use such a contact massin conjunction with a novel converter in which heat exchange elementsare arranged and constructed in relation to the contact mass, or ratherthe volumetric heat capacity of the contact mass, so as to effectefficient heat control. We have found that, by using a combination ofindirect heat exchange elements and a contact mass of selected heatcapacity, such controlled heat capacity being obtained by usingcontrolled proportions of catalyst and high heat capacity material or byusing a single material having both catalytic and high heat capacityproperties, the heat exchange elements may be of simple design andarrangement. These features in combination with other features of theinvention pointed out in the following detailed description, provide aconverter from which the contact mass can be discharged speedily andsimply.

In carrying out the process of our invention for cracking hydrocarbons,We prefer to operate so that the coke deposit as specified below is lessthan 5.8 grams per liter of contact mass per each ten minutes ofcracking time. Such a coke deposit is produced while maintainingconditions of cracking that are included in the ranges; 700 to 950 F.and preferably in the range 750 to 900 F. about the atmospheric topounds per square inch gauge pressure and preferably about atmosphericto 50 pounds per square inch gauge; space rates of about 0.4 to 8volumes of liquid oil per hour per volume of solid catalyst present inreactor and preferably 0.5 to 4 space rate; and amounts of added steamranging from 0 to about 25 weight per cent of the charge stock. Any orall of the more severe conditions of cracking (higher temperatures,higher pressures, low space rates and a small amount, if any, of addedsteam) are used for more refractory or lower boiling stocks. The higherconditions of temperature can be used where a high content of arcmaticor olefinic material in the product is desired. In general, the variouscondition of cracking are interrelated and it is within the scope of ourinvention to vary any or all of these factors in order to produce adesired severit of cracking as indicated by the amount of coke deposit.

The invention can be more easily understood by a consideration of thdrawings which illustrate specific embodiments of the invention asapplied to the particular example of catalytic cracking.

In the drawings:

Figure 1 is a vertical section of an assembled converter, takengenerally along line I-I of Figure 2. For clearer understanding, theconverter is illustrated somewhat diagrammatically and process fluiddistributing conduits and heat exchange elements are shown both insection (right hand side) and in full (left hand side) While a fin hasbeen omitted from each of the heat exchange elements in the full view.

Figure 2 is a horizontal section of the assembled converter, taken alongline 2-2 of Figure 1. To simplify the drawings, process fluiddistributing conduits and the heat exchange elements have been omittedin the upper portion of Figure 2, although the converter, in operation,would be completely filled with such conduits and elements. Thearrangement of process fluid distributing conduits and heat exchangeelements in Figure 2, as in Figure 1, is schematic; examples of actualarrangements being shown in Figures 5 and 6.

Figure 3 is an enlarged vertical section of the details of a processfluid distributing conduit or distributor of the type that communicateswith the upper process fluid manifolding chamber.

Figure 4 is an enlarged vertical section of the details of process fluiddistributing conduit or distributor of the type that communicates withthe lower process fluid manifolding chamber.

Figure 5 is a horizontal section of a unitary pattern of arrangement ofboth types of distributors and of heat exchange elements.

Figure 6 is a horizontal section of an alternate unitary pattern ofarrangement of distributors and modified heat exchange elements.

Figure '7 is a horizontal section of a portion of the boundary zone of aconverter wherein the heat exchange elements have been modified toprovide for the abnormal conditions in that zone.

Figure 8 is a representation of a type of contact mass which we use incombination with our converter.

Referring to Figures 1 and 2 the converter consists of a cylindricalcasing shown generally at I which may be provided with an outer covering(not shown) of heat insulating material. The converter is divided bytube sheets H, I2, 13 and I4 into various chambers or process zones.

A top tube sheet II and a contact mass retaining tube sheet I2 define achamber I in which a contact mass M is placed in accordance with ourinvention and whose nature will be described -more fully below. The toptube sheet forms with the removable top of the casing It an upper-;process fluid manifolding chamber I7; the contact mass retaining tubesheet I2 and the main tube sheet I3 define a lower process fluidmanifolding chamber I8; the main tube sheet I3 and the bottom tube sheetI4 define an upper heat exchange fluid manifolding chamber I9; and thebottom tube sheet I4 and the bottom of the casing 20, which may beremovable, define a lower heat exchange fluid manifolding chamber 22.The top tube sheet II and the bottom tube sheet I l are held between thecooperating flanges of the casing Ii] and the top I6 and the bottom '20respectively. Within the chamber I5 for the contact mass, there areplaced distributors 21, communicating with manifolding chamber I1, anddistributors 32, communicating with manifolding chamber I8, for theintroduction, distribution and removal of process fluids to and from thecontact mass placed within chamber I5. Also within chamber I5 are heatexchange elements 33 for the circulation of an indirect heat exchangefluid to control the temperature of aforesaid contact mass. Spacers 23and 2| rest on tube sheet I3 and thereby space and support tube sheetI2, spacer 23 forming the vertical wall of the lower process fluidmanifolding chamber I8,

A shell 24 which, as seen in Figures 2 and 7-, is shaped to conform tothe outer boundary of the pattern of distributors and heat exchangeelements, is placed within thecontact mass chamber I5. Shell 24 isattached to the casing by means of bolts IE! which hold the shell 24 inplace and space the shell from the casing I0, thereby providing a spacefor insulation 25. The shell 24, which is preferably of light metal SOthat it can be easily formed into the appropriate shape, may be securedto tube sheet I2 so as to prevent the passage of fluids through theinsulation 25. The insulation 25 may be any appropriate material but ispreferably relatively impenetrable, such as insulating concrete. Themain tube sheet I3, which is transversely disposed within the casing II)in spaced relation between the contact mass retaining tube sheet I2 andthe bottom tube sheet I4, is sealed in a suitable manner, as by welding,to the inner periphery of the casing Ill. Process fluids can be passedin and. out of the casing It! by means of a port 26 in the removable topIt of the casing. Distributors 2'5, one of which is described in greaterdetail in connection with Figure 3, extend through the upper tube sheetI! and are held in position by means of plates 28. These distributorsare removably attached to the contact mass retaining tube sheet I2 bythreaded closure plugs 29. To aid in an even distribution of processfluids into or from the contact mass M, the distributors are providedwith metering orifices 38. Process fluids are also passed to and fromthe contact mass by distributors 32 which are removably attached to thecontact mass retaining tube sheet I2 as shown in Figure 4 and areprovided with metering orifices 3! in a similar manner to distributors21. Conduits 38, for the passage of process fluids in or out of theconverter, pass through the two indirect heat exchange fluid manifoldingchambers I9 and 22 and communicate with the lower process fluidmanifolding chamber I8. These conduits extend through the bottom of thecasing 20 to suitable apparatus for additional treatment or use of theprocess fluids. The up-- per ends of conduits 38 are rolled into themain tube sheet I3 or otherwise suitably secured or attached thereto.Any liquid that accumulates in chamber I8 may be drained out by conduits38. Conduits 38 may be eliminated, if desired as when drainage ofprocess liquids is not necessary, in which event the process fluids areintroduced to or removed from manifolding chamber l8 by ports 42.

From what has been said above, it will be seen that process fluids maybe passed through the converter either from top to bottom or from bottomto top by means of the elements shown. When the converter is beingemployed for cracking hydrocarbon oils, the process fluids, whichcomprise the oil in vapor form during the reaction period and air orother oxidizing gas during the regeneration period, are preferablycaused to flow through the converter in the following manner. ducedthrough conduits 33 whence it flows successively through the chamber l8,into conduits 32, through perforations 3!, and into contact mass M. Thefluid leaves the converter through perforate conduits 2?, chamber H andport 25. It is preferred, however, to pass the hydrocarbons through theconverter in the direction described, and to pass the oxidizing gasthrough in the reverse direction.

To carry a heat exchange medium in indirect heat exchange relationshipwith the contact mass, heat exchange elements, in the form ofimperforate conduits 33, are provided. The open lower ends of the heatexchange elements 33 are rolled into holes in the main tube sheet E3 andextend through the lower process fluid manifolding chamber I8 into thecontact mass chamber I with their closed upper ends 36 in proximity tothe top tube sheet H. In the particular design illustrated in Figures 1and 2, flns 34, which provide a controlled amount of heat exchangesurface, are welded longitudinally along the outer periphery of heatexchange elements 33 for substantially the verticalextent of the portionof the heat exchange elements within the contact mass. Placed withineach heat exchange element 33 and spaced therefrom by spacers (notshown), is a conduit of smaller diameter 35 whose open lower end isrolled into the bottom tube sheet [4 and whose open upper end is inproximity to the closed upper ends 36 of the heat exchange element 33.Orifice plates 37 are placed within the open upper ends of conduits 35in order to increase the resistance to the flow of heat exchange fluidand, by the consequent increase in pressure drop, to minimize the effectof varying resistance to rlow in the various conduits and thus insurethe even distribution of heat exchange fluid to the various conduitswithin the casing.

The temperature of the converter and its contents is regulated by meansof an indirect heat exchange fluid circulated in indirect heat exchangerelationship with the contact mass and through tubes or conduits placedaround the exterior of the casing. Heat exchange fluid in line 4| ispumped by pump :14 through throttling valve 45 and line 46 to a header4?, which extends, as shown in Figure 2, in a circular fashion aroundthe exterior of the case. The heat exchange fluid flows upwardly throughconduits 48 to an upper header 49 from which it is removed by linelifi.

I Tubes or conduits 18 are placed in direct contact with the exterior ofthe casing and may be flattened to insure better contact. Tubes 48 maybe welded or secured by other means to the exterior of the casing if sodesired and serve to maintain the exterior wall of the casing atsubstantially the temperature of the heat exchange medium which is alsocirculated within the cham- Either fluid may be alternately introchamber22, its flow being adjusted by means of throttling valve 53. The heatexchange fluid then passes up conduit 35, through orifice 31, and downthe annular space between elements 33 and to the upper heat exchangefluid manifold l9. During its passage through the portion of the heatexchange element within the chamber l5 for the contact mass, andparticularly during its downward passage in contact with the innerperiphery of heat exchange element 33, the heat exchange fluid is inindirect heat exchange relationship with both the contact mass and heatconducting fins 35. The heat exchange fluid passes out of chamber itthrough ports 54 and line 55 and can be returned, together with similarfluid from the header 49, to the pump 44. The heat exchange fluid can beadjusted in temperature by heat exchangers placed at any point in itsflow outside of the casing. Vents 56 and 51, communicating with themanifolding chamber l9 and with the header &9 respectively, furnish ameans of venting the heat exchange system to remove gases which mightinterfere with the circulation of heat exchange liquid.

Any suitable type of fluid heat exchange medium may be used forcontrolling the temperature of the contact mass and the exterior wall ofthe casing. The heat exchange fluid can be a single phase compositionwhich does not or is not permitted to vaporize, including fused saltssuch as the alkali nitrates or nitrites or eutectic mixtures of thesematerials such as disclosed in U. S. P. 2,375,761, granted May 15, 1945,to John R. Bates. Certain metals and metallic alloys may be used, ormaterials which undergo a change of state as by vaporization. Water,diphenyl, mercury, chlorinated hydrocarbons or other inert liquids canbe used in the liquid, vapor or mixed phase state. The flow orcirculation of the heat exchange fluid can be regulated or stopped ineither the heat exchange elements in the con 1: tact mass or the heatexchange tubes fastened to the exterior of the case by means of valves45 and 53. As previously mentioned, orifices 31 compensate for anyinequality in the length or pressure drop in conduits 35 and act toprevent inadequate flow of the fluid in longer or obstructed conduitsand thereby insure an even distribution of heat exchange fluid throughall of the conduits with an ensuing evenness of temperature throughoutthe contact mass despite variations in pressure above orifice ill.

In Figure 3 is shown in detail the manner in which distributors 2! areattached to the top and contact mass retaining tube sheets I! and 2.Distributor 2?, which is a perforate process fluid distributing conduit,is closed at the lower end by a threaded closure plug 29 so that thelower process fluid manifolding chamber i5 is out of communication withthe interior of distributor 21. This closure plug is Welded inthe end oftube 2! and has a threaded extension which extends into and engages athreaded hole or aperture 15 in the contact mass retaining tube sheet52. The distributor is removably attached to the top of tube sheet H bymeans of a plate I? (indicated schematically by 28 in Figures 1 and 2)which bears on sealing ring is and is tightened by nuts '29 on boltswhich are in threaded engage ment with the top tube sheet H. When nuts19 are tightened the plate Tl bears against ring 18, which may be of anysuitable packing material that willstand' high temperature and ispreferably metallic such as stainless steel. Plate 1'! is madeof acorrosion resistant metal such as stainlesssteel and is designed toprovide a clearance space 83 between distributor 2? and plate ll. Theaperture in tube sheet 1 I through which distributor 21 passes issomewhat larger than distributor 2'! and communication is thus providedbetween the chamber 15 for the contact mass and the upper process fluidmanifolding chamber I! by clearance 83 which provides a metered flow.Clearance 83 acts similarly to orifices, 38 by controlling the amount offlow of process fluids to and from the contact mass. Orifices 30 andclearance 83 arev designed and sized to provide equal streams of processfluids relative to; the amount of contact mass traversed by thesestreams, with due consideration being given to the various pressuredrops along the path of the process fluids. Thus the sum of the flowthrough the topmost set of orifices 30 and clearance 83 provide the sameflow relative to the amount of contact mass as do the lower sets oforifices. A conventional packing may also be used in place of clearance83 in which event, all process fluids pass through orifices 3B which,accordingly are sized to give equal distribution. Welded or otherwisesecured in the top of .distributor 21 is a member 82 to which issecurely attached tube 84 as by rolling the open end of tube 84 intomember 82. As can be seen by reference to Figure 1, tube 84 forms ameans whereby fluids can be passed down tube 84, out of the open end oftube 84 at the bottom of conduit 2'! and then upwardly along the annularspace 85 between tube 34 and conduit 21 and out the metering orifices30. By using the reverse flow arrangement shown in Figure 3, thetemperatures of process fluids and of top of distributor 21 instead tothe bottom by the reverse flow arrangement of Figure 3.

In Figure 4 is shown a detailed view of distrib- V utor 32 which is aperforate process fluid distributing conduit, closed at the upper end byremovable closure plug 93. Distributor 32 is joined to the contact massretaining tube sheet [2 by means of a plug 9| which has a hexagonallyshaped aperture for the insertion of a wrench. Distributor 32 is weldedor otherwise suitably attached to plug 9! and the assemblage is thenthreaded into the contact mass retaining tube sheet i2. Also secured tothe plug Si is an inner tube 92 which serves to convey the processfluids to the upper end of distributor 32 and operates in a similarmanner to tube Ed in distributor 21. The metering orifices 3! indistributors 32 are placed at levels which alternate with the levels atwhich the metering orifices 39 in distributors 21 are placed.

Distributors 32 and 21 form two sets of perforate conduits which serveto introduce and remove the process or reactant fluids to and from thecontact mass. Distributors 21, which communicate with the upper processfluid manifolding chamber Ii, will be designated, for convenience. as Btubes and distributors 32. which communicate with the lower processfluid manifolding chamber I8, as C tubes. Thus, by placing the meteringorifices at diflerent levels in the B and C tubes, the contact mass is,in efiect, divided into separate horizontal sections, through each-oi?which the process fluids flow in parallel. Thus, levels in the contactmass may be considered as being spaced equidistantly in a sequence, I,2, 3 4, 5, 6, where l and 6 are the top and bottom of the contact mass.The orifices in a B tube can be placed at levels I, 3. and 5 and theorifices in a C tube at 2, 4, 6. In a converter designed as shown inFigures 1 and 2 We prefer to space the metering orifices so that thedistance between the orifices in a single tube is between 4 and 20,feet, thus dividing the contact mass into 2 to 10 foot sections.However, other lengths of path through the contact mass, such as lengthsof path as short as 6 inches, or as great as 15 to 20 feet, may be usedwhere the conditions render such lengths of path desirable.

The arrangement of the fluid distributing conduits and the heat exchangeelements is an important feature of the structure of the converter and,in accordance with the invention, is related to the type of contact massemployed. We have found that use of the contact masses described belowtogether with arrangements of distributors and simplified heat exchangeelements, such as those illustrated in Figures 5 and 6, provide superiortemperature control of the contact mass with ensuing process advantageswhile providing for a quick and complete discharge of the contact mass.As noted above, the preferred unitary patterns of arrangement are shownin Figures 5 and 6. Figure 5 illustrates a unitary pattern in which adistributor 21, in communication with the upper process fluidmanifolding chamber I1, is placed at the center of a rectangle at thecorners or vertices of which are placed distributors 32 which are incommunication with the lower fluid process manifolding chamber.Distributor 2! is also the center of a hexagon at Whose vertices arearranged heat exchange elements 33. On the outer periphery of the heatexchange elements 33 are fins 34 which, in the embodiments illustratedin Figures 5 and 6, are rectangular in transverse section and attachedlongitudinally to the heat exchange elements by some suitable means suchas welding. Fins 34 may be formed integrally in the manufacture of theheat exchange elements 33 or may be attached subsequently or, instead ofbeing solid metallic members as shown in Figure 5, may be hollow andfilled with the indirect heat exchange fluid which circulates throughthe heat exchange element 33. Fins 35 extend radially from the verticalaxis of the heat exchange element and are spaced approximately apart inthe embodiment shown in Figure 5. In the unitary pattern of Figure 5,the fins in each case are directed toward one of the distributors.Removal of one of the freely rotatable distributors, either of the type21 or 32, leaves an aperture in the contact mass retaining tube sheet 12to which these distributors are removably attached (see Figures 3 and4). The contact mass disposed between the heat exchange elements andtheir fins can then flow downwardly and out of the contact mass chamberl5 through such an aperture. The unitary pattern shown in Figure 5 isarranged and disposed so that the fins permit downward and lateral flowof contact mass from around several tubes toward a single aperture inthe tube sheet formed by removal of a distributing conduit. We havefound that removal of every distributor is not necessary and the contactmass will discharge quickly and completely when approximately 20% of thedistributors are removed. It should be noted that, as the unitarypattern is repeated, distributor 21, which is the center of the unitarypattern illustrated, becomes the corner of a rectangle of similardistributors 21 in the center of which is distributor 32, surrounded bya hexagon of heat exchange elements. If the terminology of Figures 3.and 4 is used, the chamber for the contact mass is filled with two setsof d.stributors, identified as B and C tubes together with heat exchangeelements which may be designated as K tubes. The perforate conduits arearranged in an interlocking pattern such that each B tube is at thecenter of a quadrangle at the corners or vertices of which there arefour C tubes, while each C tube is at the center of a quadrangle at thecorners or vertices of which there are four B tubes, each C and B tubebeing located at the center of a hexagon at the vertice of which thereare six K tubes. The relationship of the contact mass M to the unitarypattern is shown by the circular section in Figure 5, an enlargement ofwhich is shown in Figure 8.

In Figure 6 is shown another method of the arrangement of the fins onthe outer periphery of heat exchange elements 33. Figure 6 illustrates aunitary pattern with a distributor 32 as the center of a hexagon at thealternate vertices of which are heat exchange elements having sixinstead of three fins, the fins thereby being 60 apart. It should benoted, however, that this arrangement still does not interfere with theproper flow of the contact mass toward the apertures formed by theremoval of the distributors.

The above features of our converter permit an easy and completedischarge of a granular contact mass in the following fashion. When thecatalyst has deteriorated past the point where the hydrocarbon chargestocks available can be economically processed, the converter is purgedof combustible vapors and allowed to Cool to a temperature which permitshandling of the equipment. The removable top it is taken off and the toptube sheet H is removed after unscrewing nuts 19 and removing plates 71.The vertical walls of the lower process fluid manifolding chamber i8formed by spacer 23 are provided with a plurality of apertures used inconnection with the discharge of the contact mass. These apertures areprovided with closure plugs 40 and communicate with ports 42 placed inthe wall of the casing l0. Ports 42 are provided with pressure .tightcovers 43 which, together with closure plugs 40, ar kept in place duringthe normal operation of the converter and are removed for the dischargeof the contact mass. After removing covers 43 and plugs 40, some of thedistributors of both types, 21 and 32, which are freely rotatablewithout interference with any of the other structures in the reactionchamber i even when the contact mass is in the reaction chamber, aredsengaged from the catalyst retain'ng tube sheet i 2 and the catalystallowed to discharge through the resulting apertures in tube sheet 12into chamber 18 and thence through conduits 38. Alt/ernately, part orall of the contact mass may be removed from chamber [9 through ports 42.

During the period when the chamber is being filled with the contactmass, the tops of heat exchange elements and distributing conduits canbe held in place by spacers which may be removed before the top tubesheet H is replaced.

The above described procedure for discharging and recharging contactmass has decreased the time consumed by this operation by as much asfour fifths of that previously necessary. This 10 decrease in oiT-streamtime represents considerably improved commercial operation. In Figure 7is shown a modified pattern or arrangement of the two sets ofdistributors and the heat exchange elements at the boundary of thereaction zone. At the boundary, unusual conditions of temperature mayoccur. ample, in catalytic cracking operations, we have found that localoverheating is sometimes encountered near the reactor shell. Such localoverheating causes excessive deposition of coke on the catalyst withinthe zone affected. Upon burning, the excess of coke results inincreasingly higher temperatures, even to the point of damaging eitheror both the catalyst and adjacent metal structure. To eliminate thesedifficulties, we employ lower volumetric concentrations of catalystadjacent the boundary of the reaction zone than in the remainder of thereaction zone, while simultaneously increasing the heat capacity of theboundary portions thus modified. Thus, the ratio of heat capacitymaterial to catalyst or the volume of the heat conducting fins attachedto the heat exchange elements or both may be increased. In some cases,it is desirable to omit the catalyst completely from a small portion ofthe reaction chamber adjacent the boundary and use only refractorymaterial. Figure 7 illustrates one method of improving the temperaturecontrol at the boundary of the reaction zone. The fins attached to heatexchange elements 33 are increased in volume in the manner shown by fins95. Where the heat exchange elements are close to sheet 24 which formsthe boundary, a short stubby fin 96 can be used. As shown in Figure 7,various arrangements of the more massive fins and 96 can be used. Thesemore massive fins have the eiiect of decreasing the temperature gradientalong their radial extent with the result that the adjacent contact massis more effectively cooled. However, these fins still are designed sothat they do not obstruct the fiow of contact mass when it is'discharged from the bottom of the reaction zone.

One of the features of the invention is the contact mass used inconnection with converters similar to that described above. We havefound that contact masses having at least 0.45 British thermal unit perliter per degree Fahrenheit permit greatly improved converter design andoperation. (The volumetric heat capacity, as used throughout thisspecification, is calculated as the product of the speciic heat,measured at the temperature of operation, times the apparent or bull;density; i. e., the weight of a unit volume of the material in the form(such as granules, pieces or pellets) under consideration.) We select orprepare the contact mass M to be used in the converter with regard toits catalytic properties and its volumetric heat capacity. We prefer touse contact masses which, when used for the catalytic cracking ofhydrocarbon material boiling above the gasoline range, produce, underthe conditions of time, temperature and pressure used in the process,gasoline to the extent of at least 30 and preferably above 40 volumepercent of the charge stock without excessive formation of gas and coke.We have found that the volumetric heat capacity of the contact mass isrelated to the heat exchange elements, particularly in regard to theextent of and average spacing or clearance between the heat exchangesurfaces. By using contact masses which havea volumetric heat capacityof at least 0.45 British thermal unit per liter per degree Fahrenheit(B. t. u./li-

For exl 1 ter/FJ, we can space adjacent non interscting heat exchangesurfaces to provide clearances averaging an inch to two'inches orgreater, with a'consequent simplification of converter design. Suchclearances provide not only easy discharge, but also dense packing ofthe contact mass and hence efficient utilization of the space availablefor the contact mass. Thus, a comparison of the packing of contactmasses in converters cons'tructed with various clearances between thesur faces of the heat exchange elements showed that the contact massoccupied the space available one type of our novel converter (clearanceover 1 /4 inches) almost completely (99%) whereas a similar contact masspacked in a converter having average clearances of approximately of aninch occupied only 90% of the available space. We have found thatconverters employed catalytic cracking having heat exchange ele inentsconstructed and arranged to have clearances averaging an inch or over,such as 1 /4 to 2" inches, when used in conjunction with contact masseshaving volumetric heat capacities of over 0.45 B. t. u./liter/F., showexcellent temperature control when heat exchange surfaces of between 0.3and 0.7 square foot per liter of contact "mass are provided. We havealso found that by increasing the volumetric heat capacity of thecontact mass to 0.5 B. t. u./liter/F. or higher, we can further increasethe clearances between nonadjoining surfaces of heat exchange elementsto values such as average clearances of about 2 inches and greater,and/or use intermediate values of the ratio of the heat exchange surfaceto contact mass, such as 0.4 to 0.6 sq. ft./liter of contact mass. Evenwith the increased clearances, thermal control of the contact mass isexcellent and low thermal gradients are encountered within the mass.

One form 'of the contact mass, according to our invention, comprises amixture of porous solid surface active material or catalyst and in ertrefractory and preferably nonep'oro'us material for heat capacity, thenature and proportions of which will be hereinafter described. Themixture of the two materials may be a mixture of particles of the twomaterials, the sizes of the particles being selected to obtain themaximum average dispersion of one material in the other, or the mixturemay be more intimate and may be obtained by forming aggregates of theproper size from a mixture of finer materials. As examples of thelatter, an active clayv may be mixed with a fine powder of a materialhaving adequate volumetric heatcapa-city and the resultant mixtureextruded, formed into pellets and baked to harden the composite mass, ora fine powder of an inert refractory material may be added to asynthetic inorganic gel before or during the gelation stage, and theresulting gel formed or cast in the form of beads or pellets or the twomaterials may be mixed in powder form and pelleted with a pelletingmachine. The contact mass is used in the form of particles of such sizethat the contact mass fills the converter evenly and as completely aspossible. We use particles or pieces of between 1 and 10 millimeters insize but preferably between 3 and 7 millimeters, the larger sizes beingmore adapted. to converters having larger average clearances,

'such as 2 inches or greater, and to the type of contact mass in whichboth a catalyst and an inert refractory material are incorporated in asingle piece.

When the invention is employed in connection attics-ihave an adversecatalytic effect.

32 with catalytic cracking or hyarecarb n mat the" porous solid surfaceac'tive material p propriately a cracking catalyst of natural or en};thetic origin. Among the various catalysts which can be used are naturalor synthetic active al'uminosilicates such as clays containing clayminerals such as montmorillonite, and the like which may be activated byacid or alkaline treat-#- ment, or synthetic silica-alumina,silica-'zirconia or sili'ca alumina-zirconia gels. Other suitablecatalysts are silica-urania gels, silica tho'ria gels, zirconiumphosphate and the like. An inert refractory material should be selectedwhich does not react chemically with the catalyst or with the fluids tobe contacted or produced by the process, and which can withstand thetemperatures used in the process without physi cal change ordeterioration and which hasaa adequate volumetric heat capacity. Whenthe invention is used in connection with catalytic cracking, thspecifications of the inert refrac t'ory material should includeabilityto withstand temperatures of l000 to 2000 F. and preferably above 1200F., and a volumetric heat capacity of greater than 0.6 British thermalunit per liter per degree Fahrenheit (measured at the operatingtemperature) although heat capacities in the range greater than 0.8 B.t. u./liter/ F. are pre* ferred. In general, suitable materials aredense preferably non-porous materials with specific heats of greaterthan 0.20 and preferably above 0.25 (measured at the mean temperature ofoperation of the process). Suitable materials include various oxides ofthe second, third and fourth groups of the periodic table, for example,alumina, silica, beryllia and zirconia. Preferred forms of thesematerials, which possess the desired characteristics of cheapness,availability and high heat capacity, include corundum, fused quartz,magnesia, mixtures of these materials, and commercial modifications ofthese materials such as sand, Alund-um, Corhart and the like. The inertrefractory solid may consist of one or more components and it may beprepared by fusion, precipitation, gelation or other methods. I 'nfusible metals can be used in the free state, but the metal should beselected so that itdoes not Various suric'ates, carbides, dead burnedores, natural refractories, crushed igneous rocks, dense or fused in"-act'i've clays, and the like may also be used. Thus,

a suitable material can be selected for the various modifications ofthis invention in accordance with the conditionsof operations or themate'- -rials used in the modification.

When a mixture of catalyst and inert refractory mate'rialis used for acontact mass forcatalytic cracking, presently commercially availablecatalysts are generally materials having volumetric heat capacityofabout 0.35 to 0.42 B. t, u;/

liter/F. In such a case, an appropriate mix ture consists of about 40 tovolume percent .of the catalyst and about 60 to 10 volume percentcontact mass such as is described above. The dark particles 98 arecrushed and sized particles of an inert refractory material such as isobtained by the fusion of a mixture of refractory oxides such as silica,alumina and zirconia. The pellets 99 are molded pieces of a synthetic ornatural porous solid catalyst. The contact mass can be a single materialwhich has the proper heat capacity and catalytic activity. In such aform, the contact mass may be a natural product, which may have beenchemicallytreated to produce the desired characteristics or may be asynthetic product, such as an inorganic hydrogel, which, either by themethod of formation of the gel or by subsequent processing, has adensity and a specific heat such that its volumetric heat capacity isgreater than 0.45 B. t. u./liter/ E. Additional advantages are realizedwhen contact masses of whatever origin are used which have a higher heatcapacity such as 0.5 B. t. u./liter/ F. or above.

We have found that the use of contact masses as described above enableus to employ a converter of simplified design which has considerableadvantages in the ease of discharge of the contact mass and yetmaintains and even surpasses the performance of more intricate andcomplex converters in regard to temperature control and processingcapacity. The following example illustrates an application of ourinvention and advantages thereof.

EXAMPLE A converter A, embodying the principles of the unitary patternof process fluid distributing conduits and heat exchange elements shownin Figure 5, was constructed and filled with a contact mass whichcomprised a mixture of 72 volume per cent of pellets, 4 mm. in size, ofa synthetic cracking catalyst composed of silica and alumina and 28volume per cent of crushed pieces of about the same size of a commercialrefractory material known as Corhart (a fused alumina containing about25% silica). The volumetric heat capacity of the contact mass wascalculated to be .55 B. t. u./liter/F. at 1000 F. lhe converter, whichwas cooled by indirect heat exchange with a molten mixture of inorganicsalts, had an average clearance of about 2% inches between adjacentnonintersecting surfaces of heat exchange elements and had a ratio of0.45 square foot of heat exchange surface per liter of contact mass. Inorder to evaluate the utility of converter A, hydrocarbon charge stocksof varying boiling ranges and from various types of crudes were crackedin converter A. Similar stocks were cracked in a converter B, which alsoused a molten salt heat exchange system. Converter B had over twice theratio of heat exchange surface to contact mass (1.2 square feet perliter of contact mass) as did converter A and had average clearancesbetween the heat exchange surfaces or fins of approximately of an inch.Converter B Was filled with a contact mass comprising only syntheticcracking catalyst of the same type and activity as used in converter A.The timing cycle used in the cracking operations was 10 minuteson-stream (cracking phase), 10 minutes for burning off coke by air(regeneration phase) and two 5 minute periods between the alternateon-stream and regeneration periods for valve changes and purging.

The results of cracking the various charge stocks showed that theprocess using converter A at least equalled the process using converterB in regard to quality and quantity of products at equal or greaterthroughputs while having superior temperature control of the contactmass. The data below in Table I are illustrative of the results and wereobtained from cracking operations on similar heavy gas oil fractionsfrom an East Texas crude oil; the process listed under converter B beingperformed under typical commercial conditions of charging rate of feedstock and amount of coke deposit, other conditions being adjusted toobtain a high conversion of charge stock to motor gasoline. Runs inconverter B, the results of one of which are shown in Table I, provedthat a higher charging rate, relative to the catalyst, could bemaintained in converter A than in converter B at the same level ofconversion of charge stock to motor gasoline.

Table I Process using Yields 1 Con- Converter A i verter B Spacevelocity (Volumes of liquid charge stock (at 60 F.) per hour volume ofcatalyst present in reactor) 1.25 l. 1 Motor gasoline, vol. per cent 42.0 42. 2 Octane Number (AS'IM), clear 78. 9 78.8 Liquid recovery, vol.per cent 90. 4 87.0 04, weight per cent 8.0 9. 6 C3 and lighter, weightper cent. 4. 6 6. 3 Coke, weight per cent of charge 4. 4 4. 3 Coke,grams coke/liter contact mass 5. 7 6. 9

1 Based on 10 pounds Reid vapor pressure.

The results in Table I show that the process conducted in our novelconverter A showed a higher liquid recovery and a lower percentage ofless desirable light gases than did the process conducted in converter Bat the same level of conversion of charge stock to motor gasoline andcoke. Moreover, converters of the type of converter A have a 35 to 40%higher volumetric efficiency than converters of the type of B (wherevolumetric efficiency is based on the amount of contact mass per unitvolume of converter) due to the simplification of converter design andimproved packing of the contact mass. Thus, as shown by the 14% increasein charging rate for converter A, in our improved converters, we have ahigher throughput or processing capacity for the same size of converterwhen using contact masses having ratios of catalyst to inert material of2 /2 or 3 to 1 and above while at even lower ratios we can maintain atleast equal throughput at the same time that we have the aboveadvantages.

Further investigation showed another feature of our invention. Whenconverter A is used for a cracking operation, the temperature variationof the contact mass is less than that in converter B when the sameamount of coke per unit of catalyst is involved. Since the amount ofcoke burned per cycle governs the heat liberated per cycle, slightlymore heat was removed by the indirect heat exchange fluid from converterA than was removed from converter B with less variation in the averagetemperatures of cracking and regeneration, even though converter B hadover twice as much heat exchange surface per unit volume of catalyst ofcontact mass. The following data were observed in the two convertersduring runs at the same space velocity with the same charge stock andusing the same timing cycle and contact masses described above.

Table I1 Convert- Converter A er B Coke deposited, grams/liter catalyst7. 7 7.0 Temperature rise of contact mass above minimum crackingtemperature, F.:

0-2 minutes (regeneration) 51 128 0 69 196 0-6 105 155 0-8 115 116Difierence between In regeneration and minimum temperature of crackingof contact mass, F 115 197 Maximum temperature of regeneration ofcontact mass for cracking temperature of 850 F. 956 l, 034 Temperaturediilerence between contact mass and indirect heat exchange fluid, F. atend of cracking period 42 0 The operation in converter A resulted inmuch lower maximum regeneration temperature for the same temperature ofcracking and less variation between the temperatures during cracking andregeneration. As shown by the last line of Table II, the molten salttemperature is lower in converter A than in converter B for the sametemperature of conversion or cracking with resultant beneficial efiectson the molten salt system.

In a typical operation laying down 7.0 grams of coke per liter of activecatalyst, about 210 B. t. u. (-due to burning of the coke) are liberatedin every half-hour cycle of the type described above. Of this heat, 80to 90% may be removed by the indirect heat exchange system. Theremainder of the heat is used in the endothermic heat of cracking, andin raising the temperatures of the reactants and products. Excess heatis thereby removed from the contact mass at an hourly rate of about 370B. t. u./liter of catalyst. In cracking operations in order to limit theregeneration temperatures, we prefer to limit the coke deposit so thatstable operation results when the excess heat is removed at a rate ofthe order of 400 B. t. u. per hour per liter of contact mass; this ratebeing independent of the timing of the cycle and corresponding, in thecase of the contact mass described above in connection with converter A,to about 8 grams of coke per liter of catalyst per half-hour cycle orabout 5.8 grams of coke per liter of contact mass for the half-hourcycle. Under such conditions, the life of the catalyst is prolonged dueto low maximum temperatures of regeneration and yet adequate processingcapacity is maintained.

As will be seen from the results given above, the use of the contactmasses and converters of our invention results in several advantages.For 1 the same molten salt temperature, the on-stream temperature ishigher with a resultant increase in conversion without an increase inthe maximum regeneration temperature. If high conversion temperaturesare desired in converters of other designs. the salt temperature must beraised and the system containing the molten salt thereb having resultanttendency toward accelerated metal corrosion. The lower regenerationmaximum reduces the temperatures to which metals within the converterincluding conduits are subjected with a resultant beneficial effect onthe useful life of the converters. Considerable advantage can be gainedby use of the invention in various other types of converters,'such asthose utilizin a path of suitable length straight through the entiredepth of contact mass instead of a plurality of paths such as providedin the converters of the drawing.

Inasmuch as many modifications and variations 16 of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, only such limitations should be imposed on the inventionas are indicated in the appended claims.

We claim as our invention: 1. In a cyclic process for the catalyticcracking of hydrocarbons using a static bed of catalytically activecontact material which process comprises an endothermic cracking period,during which said bed of catalytically active contact material iscontacted with said hydrocarbons and concomitantly accumulates acarbonaceous deposit, and an exothermic regeneration period, duringwhich said carbonaceous deposit on the contact mass is removed byoxidation; the improvement which comprises passing said hydrocarbonsunder cracking conditions through a bed of selected heat capacity of atleast 0.45 British thermal unit per liter per degree Fahrenheit, saidcontact mass consisting of from 40 to percent of siliceous hydrocarboncracking catalyst and from 10 to 60 percent of an inert refractorymaterial of high volumetric heat capacity, and continuously removingheat from said contact mass during the entire cracking and entireregeneration periods by fiowing heat exchange fluid at a temperaturesubstantially lower than that of the contact mass at any time through aplurality of indirect heat exchange zones regularly arranged and spacedapart within said bed, said heat exchange zones extending horizontallyand vertically into said bed and having between 0.3 to 0.7 square footof heat exchange surface per liter of contact mass, the boundary betweensaid heat exchange zones and said bed being devoid of protuberancesrestricting downward and lateral flow of said contact mass to dischargepoints at the bottom of said bed.

2. The improvement of claim 1 in which said contact mass consists ofdiscrete particles of between 1 and 10 millimeters in size andconsisting of an intimate mixture of said catalyst and said inertrefractory material in the form of a powder.

3. The improvement of claim 1 in which the peripheral portion of thehorizontal cross section of said bed contains less catalyst per unitvolume throughout the vertical extent of said bed than does theremainder of said bed.

4. Apparatus for contact treatment of process fluids at controlledtemperatures comprising a vertical casing with a removable top, a top;tube sheet and a contact mass retaining tube sheet transversely disposedwithin said casing, the top tube sheet being removable and forming inconjunction with the removable top of the casin an upper process fluidmanifolding chamber, the contact mass retaining tube sheet being inparallel spaced relation to said top tube sheet and forming inconjunction therewith a chamber. for a contact mass, said contact massretaining tube sheet forming the top of a lower process fluidmanifolding chamber spaced immediately therebelow, process fluiddistributing conduits within the casing communicating with the upperprocess fluid manifolding chamber and removably attached to the top tubesheet and extending through the vertical extent of the chamber for thecontact mass, said conduits havin closed lower ends and being threadedinto openings in the contact mass retaining tube sheet but out ofcommunication with the lower process fluid manifolding chamber,additional process fluid distributing conduits positioned within thechamber for the contact mass and with closed top ends in proximity tothe top tube sheet and with open lower ends threaded in openings in thecontact mass retaining tube sheet and communicating through open bottomends with the lower process fluid manifolding chamber, both of the abovetypes of conduits being freel rotatable about their vertical axiswithout interference with other portions of the structure or with thecontact mass and being apertured with metering orifices at variouspoints, indirect heat exchange fluid conduits with closed ends inproximity to the top tube sheet and with open lower ends fastened to themain tube sheet, said indirect heat exchange fluid conduits extendingthrough and peripherally sealed to the contact mass retaining tubesheet, the portion of said indirect heat exchange fluid conduits withinthe reaction chamber having fins on the outer periphery thereof forsubstantially the vertical extent thereof, said fins being arranged anddisposed to allow substantially complete and easy downward discharge ofa granular contact mass toward said openings in the contact massretaining tube sheet provided by removal of only a fraction of saidprocess fluid distributing conduits and having no obstructions to thelateral flow of contact mass outwardly from said indirect heat exchangeconduits, said indirect heat exchange fluid conduits and said finsconstituting heat exchange elements having an outside surface of between0.3 to 0.7 square foot per liter of contact mass and having averageclearances of greater than one inch between adjacent surfaces, means forcirculating a heat exchange fluid through said indirect heat exchangefluid conduits, conduits for the flow of process fluids to be contactedwhich extend outside the casing and communicate with the lower processfluid manifold, the removable top of the casing being provided with aport communicatin with the upper process fluid manifold, the casingbeing provided with ports communicating with the lower process fluidmanifold and having removable pressure tight covers.

5. The apparatus according to claim 4 in which the indirect heatexchange fluid conduits are circular tube and the fins on the outerperiphery thereof have a substantially rectilinear transverse sectionand extend radially from the axis of said circular tube and are arrangedto provide clearances of greater than one inch between adjacent fins.

6. In apparatus for treatment of process fluids with granular contactmass at controlled temperatures which apparatus comprises a contactingchamber defined by upper and lower horizontal tube sheets and adapted tocontain a granular contact mass, upper and lower process fluidmanifoldin chambers disposed immediately above and below said contactingchamber and horizontally coextensive therewith, two sets of perforatedprocess fluid distributing conduits within the contact mass chambercommunicating with the upper and lower fluid process manifoldsrespectively through openings in said upper and lower tube sheetsrespectively, said sets of conduits forming a means for passing processfluids from one process fluid manifolding chamber to the other processfluid manifolding chamber through a predetermined section of the contactmass, vertical heat exchange elements within the 18 municating with theupper process fluid manifolding chamber have closed lower ends, whichlower ends close openings in said lower tube sheet, and are removablefrom said openings in said lower tube sheet solely by manipulation at a10- cation above said lower tube sheet; wherein each of said heatexchange elements has fins on the outer periphery thereof forsubstantially the vertical extent thereof, said fins being arranged anddisposed to allow substantially complete and easy discharge of agranular contact mass through the openings in said lower tube sheetprovided by removal of only a fraction of the process fluid distributingconduits removably engaged therewith, said fins having no obstructionsto the lateral flow of contact mass outwardly from said indirect heatexchange conduits; and wherein all of said process fluid distributingconduits are removable and freely rotatable without interference withthe remainder of the structure and in the presence of contact mass inthe chamber.

'7. Apparatus for treatment of process fluids with a granular contactmass at controlled temperatures comprising a vertical casing with aremovable top, a top tube sheet and a contact mass retaining tube sheettransversely disposed within said casing, the top tube sheet forming inconjunction with the removable top of the casing an upper process fluidmanifolding chamber, the contact mass retaining tube sheet being inparallel spaced relation to said top tube sheet and forming inconjunction therewith a contacting chamber for containing a granularcontact mass, said contact mass retaining tube sheet forming the top ofa lower process fluid manifolding chamber spaced immediately therebelow,a first set of process fluid distributin conduits in the contactingchamber commun cating with the upper process fluid manifolding chamberand extending through the vertical extent of the contacting chamber,said conduits having closed lower ends, which lower ends engage openingsin the contact mass retaining tube sheet so as to prevent communicationwith the lower process fluid manifolding chamber, said first set ofprocess fluid distributing conduits being engaged with said contact massretaining and said top tube sheets so as to be removable solely bymanipulation from a location above said top tube sheet,

a second et of process fluid distributing conduits in the contactingchamber havin closed top ends in proximity to the top tube sheet andopen lower ends removably engaged with the contact mass retaining tubesheet and communicating through open lower ends with the lower processfluid manifolding chamber, each of the process fluid distributingconduits of said first and second sets being freely rotatable about itsvertical axis without interference with other portions of the structureor with the contact mass and being apertured with metering orifices atvarious points, a main tube sheet positioned in parallel relation belowsaid contact mass retaining sheet and defining the bottom of the lowerprocess fluid manifolding chamber, indirect heat exchange fluid conduitswith closed ends in proximity to the top tube sheet and with open lowerends fastened to the main tube sheet, said indirect heat exchange fluidconduits extending through and peripherally sealed to the contact massretaining tube sheet, the portion of said indirect heat exchange fluidconduits within the reaction chamber having fins on the outer peripherythereof for substantially the vertical extent thereof, said fins beingarranged and disposed to allow subfstanftially hammers, and easy of,ajgranular contact nass toward said ol ifi s ,in the,contactmassretaining tube sheetprovided by removal crp'mya fraction ofsaid :first set of ,process fluid distributing conduits and having noobstructions to theilateralflow of contactmass outwardly from saidindirect heat exchange conduits said indirect heat exchangefluidconduits ments having an outside isurface of LbetWeenOB to 9.?square foot perliter of contact mass and having average clearances ofgreater than one inch between adjacent surfaces, means for circulating aheat exchange fluid through said indirect heat exchange fiuid conduits,conduits for the flow ofr process fluid to be contacted whichextendoutside the casing and communicate with the lower process fluidmanifold, the removable top of the casing being provided with a portpommunicating with the upper process fluid manifold, the casing beingprovided with ports communicating with the lower processfiuid manifoldand having removable pressuretight covers. 8. Theapparatus according toclaim '7 in which the indirect heat exchange conduits are circular andsaid fins constituting heat exchange ele- I Y ,t'ub es and th'e" onihaveasub a l rl t lin a'nd t nd r di ll iromj Maxis, i tul0e and arearrangedto proyideicl rancesof "greater than one inch betweenfadjacentfins.

.RAYMO DC. LAI SI ORGE H: KEL

JAMES E. EVANS.

, FER N E .E TEP v The following references "are er'reeard inti'ie fileof this patent; a, UNITED STATES PATENTS

1. IN A CYCLIC PROCESS FOR THE CATALYTIC CRACKING OF HYDROCARBONS USINGA STATIC BED OF CATALYTICALLY ACTIVE CONTACT MATERIAL WHICH PROCESSCOMPRISES AN ENDOTHERMIC CRACKING PERIOD, DURING WHICH SAID BED OFCATALYTICALLY ACTIVE CONTACT MATERIAL IS CONTACTED WITH SAIDHYDROCARBONS AND CONCOMITANTLY ACCUMULATES A CARBONACEOUS DEPOSIT, ANDAN EXOTHERMIC REGENERATION PERIOD, DURING WHICH SAID CARBONACEOUSDEPOSIT ON THE CONTACT MASS IS REMOVED BY OXIDATION; THE IMPROVEMENTWHICH COMPRISES PASSING SAID HYDROCARBONS UNDER CRACKING CONDITIONSTHROUGH A BED OF SELECTED HEAT CAPACITY OF AT LEAST 0.45 BRITISH THERMALUNIT PER LITER PER DEGREE FAHRENHEIT, SAID CONTACT MASS CONSISTING OFFROM 40 TO 90 PERCENT OF SILICEOUS HYDROCARBON CRACKING CATALYST ANDFROM 10 TO 60 PERCENT OF AN INERT REFRACTORY MATERIAL OF HIGH VOLUMETRICHEAT CAPACITY, AND CONTINUOUSLY REMOVING HEAT FROM SAID CONTACT MASSDURING THE ENTIRE CRACKING AND ENTIRE REGENERATION PERIODS BY FLOWINGHEAT EXCHANGE FLUID AT A TEMPERATURE SUBSTANTIALLY LOWER THAN THAT OFTHE CONTACT MASS AT ANY TIME THROUGH A PLURALITY OF INDIRECT HEATEXCHANGE ZONES REGULARLY ARRANGED AND SPACED APART WITHIN SAID BED, SAIDHEAT EXCHANGE ZONES EXTENDING HORIZONTALLY AND VERTICALLY INTO SAID BEDAND HAVING BETWEEN 0.3 TO 0.7 SQUARE FOOT OF HEAT EXCHANGE SURFACE PERLITER OF CONTACT MASS, THE BOUNDARY BETWEEN SAID HEAT EXCHANGE ZONES ANDSAID BED BEING DEVOID OF PROTUBERANCES RESTRICTING DOWNWARD AND LATERALFLOW OF SAID CONTACT MASS TO DISCHARGE POINTS AT THE BOTTOM OF SAID BED.4. APPARATUS FOR CONTACT TREATMENT OF PROCESS FLUIDS AT CONTROLLEDTEMPERATURES COMPRISING A VERTICAL CASING WITH A REMOVABLE TOP, A TOPTUBE SHEET AND A CONTACT MASS RETAINING TUBE SHEET TRANSVERSELY DISPOSEDWITHIN SAID CASING, THE TOP TUBE SHEET BEING REMOVABLE AND FORMING INCONJUNCTION WITH THE REMOVABLE TOP OF THE CASING AN UPPER PROCESS FLUIDMANIFOLDING CHAMBER, THE CONTACT MASS RETAINING TUBE SHEET BEING INPARALLEL SPACED RELATION TO SAID TOP TUBE SHEET AND FORMING INCONJUNCTION THEREWITH A CHAMBER FOR A CONTACT MASS, SAID CONTACT MASSRETAINING TUBE SHEET FORMING THE TOP OF A LOWER PROCESS FLUIDMANIFOLDING CHAMBER SPACED IMMEDIATELY THEREBELOW, PROCESS FLUIDDISTRIBUTING CONDUITS WITHIN THE CASING COMMUNICATING WITH THE UPPERPROCESS FLUID MANIFOLDING CHAMBER AND REMOVABLY ATTACHED TO THE TOP TUBESHEET AND EXTENDING THROUGH THE VERTICAL EXTENT OF THE CHAMBER FOR THECONTACT MASS, SAID CONDUITS HAVING CLOSED LOWER ENDS AND BEING THREADEDINTO OPENINGS IN THE CONTACT MASS RETAINING TUBE SHEET BUT OUT OFCOMMUNICATION WITH THE LOWER PROCESS FLUID MANIFOLDING CHAMBER,ADDITIONAL PROCESS FLUID DISTRIBUTING CONDUITS POSITIONED WITHIN THECHAMBER FOR THE CONTACT MASS AND WITH CLOSED TOP ENDS IN PROXIMITY TOTHE TOP TUBE SHEET AND WITH OPEN LOWER ENDS THREADED IN OPENINGS IN THECONTACT MASS RETAINING TUBE SHEET AND COMMUNICATING THROUGH OPEN BOTTOMENDS WITH THE LOWER PROCESS FLUID MANIFOLDING CHAMBER, BOTH OF THE ABOVETYPES OF CONDUITS BEING FREELY ROTATABLE ABOUT THEIR VERTICAL AXISWITHOUT INTERFERENCE WITH OTHER PORTIONS OF THE STRUCTURE OR WITH THECONTACT MASS AND BEING APERTURED WITH METERING ORIFICES AT VARIOUSPOINTS, INDIRECT HEAT EXCHANGE FLUID CONDUITS WITH CLOSED ENDS INPROXIMITY TO THE TOP TUBE SHEET AND WITH OPEN LOWER ENDS FASTENED TO THEMAIN TUBE SHEET, SAID INDIRECT HEAT EXCHANGE FLUID CONDUITS EXTENDINGTHROUGH AND PERIPHERALLY SEALED TO THE CONTACT MASS RETAINING TUBESHEET, THE PORTION OF SAID INDIRECT HEAT EXCHANGE FLUID CONDUITS WITHINTHE REACTION CHAMBER HAVING FINS ON THE OUTER PERIPHERY THEREOF FORSUBSTANTIALLY THE VERTICAL EXTENT THEREOF, SAID FINS BEING ARRANGED ANDDISPOSED TO ALLOW SUBSTANTIALLY COMPLETE AND EASY DOWNWARD DISCHARGE OFA GRANULAR CONTACT MASS TOWARD SAID OPENINGS IN THE CONTACT MASSRETAINING TUBE SHEET PROVIDED BY REMOVAL OF ONLY A FRACTION OF SAIDPROCESS FLUID DISTRIBUTING CONDUITS AND HAVING NO OBSTRUCTIONS TO THELATERAL FLOW OF CONTACT MASS OUTWARDLY FROM SAID INDIRECT HEAT EXCHANGECONDUITS, SAID INDIRECT HEAT EXCHANGE FLUID CONDUITS AND SAID FINSCONSTITUTING HEAT EXCHANGE ELEMENTS HAVING AN OUTSIDE SURFACE OF BETWEEN0.3 TO 0.7 SQUARE FOOT PER LITER OF CONTACT MASS AND HAVING AVERAGECLEARANCES OF GREATER THAN ONE INCH BETWEEN ADJACENT SURFACES, MEANS FORCIRCULATING A HEAT EXCHANGE FLUID THROUGH SAID INDIRECT HEAT EXCHANGEFLUID CONDUITS, CONDIUTS FOR THE FLOW OF PROCESS FLUIDS TO BE CONTACTEDWHICH EXTEND OUTSIDE THE CASING AND COMMUNICATE WITH THE LOWER PROCESSFLUID MANIFOLD, THE REMOVABLE TOP OF THE CASING BEING PROVIDED WITH APORT COMMUNICATING WITH THE UPPER PROCESS FLUID MANIFOLD, THE CASINGBEING PROVIDED WITH PORTS COMMUNICATING WITH THE LOWER PROCESS FLUIDMANIFOLD AND HAVING REMOVABLE PRESSURE TIGHT COVERS.